.\" Licensed under the OpenIB.org BSD license (FreeBSD Variant) - See COPYING.md
.TH "RDMA_GET_CM_EVENT" 3 "2007-10-31" "librdmacm" "Librdmacm Programmer's Manual" librdmacm
.SH NAME
rdma_get_cm_event \- Retrieves the next pending communication event.
.SH SYNOPSIS
.B "#include <rdma/rdma_cma.h>"
.P
.B "int" rdma_get_cm_event
.BI "(struct rdma_event_channel *" channel ","
.BI "struct rdma_cm_event **" event ");"
.SH ARGUMENTS
.IP "channel" 12
Event channel to check for events.
.IP "event" 12
Allocated information about the next communication event.
.SH "DESCRIPTION"
Retrieves a communication event.  If no events are pending, by default,
the call will block until an event is received.
.SH "RETURN VALUE"
Returns 0 on success, or -1 on error.  If an error occurs, errno will be
set to indicate the failure reason.
.SH "NOTES"
The default synchronous behavior of this routine can be changed by
modifying the file descriptor associated with the given channel.  All
events that are reported must be acknowledged by calling rdma_ack_cm_event.
Destruction of an rdma_cm_id will block until related events have been
acknowledged.
.SH "EVENT DATA"
Communication event details are returned in the rdma_cm_event structure.
This structure is allocated by the rdma_cm and released by the
rdma_ack_cm_event routine.  Details of the rdma_cm_event structure are
given below.
.IP "id" 12
The rdma_cm identifier associated with the event.  If the event type is
RDMA_CM_EVENT_CONNECT_REQUEST, then this references a new id for that
communication.
.IP "listen_id" 12
For RDMA_CM_EVENT_CONNECT_REQUEST event types, this references the
corresponding listening request identifier.
.IP "event" 12
Specifies the type of communication event which occurred.  See EVENT TYPES
below.
.IP "status" 12
Returns any asynchronous error information associated with an event.  The
status is zero if the operation was successful, otherwise the status value
is non-zero and is either set to a negative errno or a transport specific value.
For details on transport specific status values, see the event type information
below.
.IP "param" 12
Provides additional details based on the type of event.  Users should
select the conn or ud subfields based on the rdma_port_space of the
rdma_cm_id associated with the event.  See UD EVENT DATA and CONN EVENT
DATA below.
.SH "UD EVENT DATA"
Event parameters related to unreliable datagram (UD) services: RDMA_PS_UDP and
RDMA_PS_IPOIB.  The UD event data is valid for RDMA_CM_EVENT_ESTABLISHED and
RDMA_CM_EVENT_MULTICAST_JOIN events, unless stated otherwise.
.IP "private_data" 12
References any user-specified data associated with RDMA_CM_EVENT_CONNECT_REQUEST
or RDMA_CM_EVENT_ESTABLISHED events.  The data referenced by this field matches
that specified by the remote side when calling rdma_connect or rdma_accept.
This field is NULL if the event does not include private data.  The buffer
referenced by this pointer is deallocated when calling rdma_ack_cm_event.
.IP "private_data_len" 12
The size of the private data buffer.  Users should note that the size of
the private data buffer may be larger than the amount of private data
sent by the remote side.  Any additional space in the buffer will be
zeroed out.
.IP "ah_attr" 12
Address information needed to send data to the remote endpoint(s).
Users should use this structure when allocating their address handle.
.IP "qp_num" 12
QP number of the remote endpoint or multicast group.
.IP "qkey" 12
QKey needed to send data to the remote endpoint(s).
.SH "CONN EVENT DATA"
Event parameters related to connected QP services: RDMA_PS_TCP.  The
connection related event data is valid for RDMA_CM_EVENT_CONNECT_REQUEST
and RDMA_CM_EVENT_ESTABLISHED events, unless stated otherwise.
.IP "private_data" 12
References any user-specified data associated with the event.  The data
referenced by this field matches that specified by the remote side when
calling rdma_connect or rdma_accept.  This field is NULL if the event
does not include private data.  The buffer referenced by this pointer is
deallocated when calling rdma_ack_cm_event.
.IP "private_data_len" 12
The size of the private data buffer.  Users should note that the size of
the private data buffer may be larger than the amount of private data
sent by the remote side.  Any additional space in the buffer will be
zeroed out.
.IP "responder_resources" 12
The number of responder resources requested of the recipient.
This field matches the initiator depth specified by the remote node when
calling rdma_connect and rdma_accept.
.IP "initiator_depth" 12
The maximum number of outstanding RDMA read/atomic operations
that the recipient may have outstanding.  This field matches the responder
resources specified by the remote node when calling rdma_connect and
rdma_accept.
.IP "flow_control" 12
Indicates if hardware level flow control is provided by the sender.
.IP "retry_count" 12
For RDMA_CM_EVENT_CONNECT_REQUEST events only, indicates the number of times
that the recipient should retry send operations.
.IP "rnr_retry_count" 12
The number of times that the recipient should retry receiver not ready (RNR)
NACK errors.
.IP "srq" 12
Specifies if the sender is using a shared-receive queue.
.IP "qp_num" 12
Indicates the remote QP number for the connection.
.SH "EVENT TYPES"
The following types of communication events may be reported.
.IP RDMA_CM_EVENT_ADDR_RESOLVED
Address resolution (rdma_resolve_addr) completed successfully.
.IP RDMA_CM_EVENT_ADDR_ERROR
Address resolution (rdma_resolve_addr) failed.
.IP RDMA_CM_EVENT_ROUTE_RESOLVED
Route resolution (rdma_resolve_route) completed successfully.
.IP RDMA_CM_EVENT_ROUTE_ERROR
Route resolution (rdma_resolve_route) failed.
.IP RDMA_CM_EVENT_CONNECT_REQUEST
Generated on the passive side to notify the user of a new connection request.
.IP RDMA_CM_EVENT_CONNECT_RESPONSE
Generated on the active side to notify the user of a successful response
to a connection request.  It is only generated on rdma_cm_id's that do not
have a QP associated with them.
.IP RDMA_CM_EVENT_CONNECT_ERROR
Indicates that an error has occurred trying to establish or a connection.
May be generated on the active or passive side of a connection.
.IP RDMA_CM_EVENT_UNREACHABLE
Generated on the active side to notify the user that the remote server is
not reachable or unable to respond to a connection request.  If this event
is generated in response to a UD QP resolution request over InfiniBand,
the event status field will contain an errno, if negative, or the status
result carried in the IB CM SIDR REP message.
.IP RDMA_CM_EVENT_REJECTED
Indicates that a connection request or response was rejected by the remote
end point.  The event status field will contain the transport specific
reject reason if available.  Under InfiniBand, this is the reject reason
carried in the IB CM REJ message.
.IP RDMA_CM_EVENT_ESTABLISHED
Indicates that a connection has been established with the remote end point.
.IP RDMA_CM_EVENT_DISCONNECTED
The connection has been disconnected.
.IP RDMA_CM_EVENT_DEVICE_REMOVAL
The local RDMA device associated with the rdma_cm_id has been removed.
Upon receiving this event, the user must destroy the related rdma_cm_id.
.IP RDMA_CM_EVENT_MULTICAST_JOIN
The multicast join operation (rdma_join_multicast) completed successfully.
.IP RDMA_CM_EVENT_MULTICAST_ERROR
An error either occurred joining a multicast group, or, if the group had
already been joined, on an existing group.  The specified multicast group is
no longer accessible and should be rejoined, if desired.
.IP RDMA_CM_EVENT_ADDR_CHANGE
The network device associated with this ID through address resolution changed
its HW address, eg following of bonding failover. This event can serve as a
hint for applications who want the links used for their RDMA sessions to
align with the network stack.
.IP RDMA_CM_EVENT_TIMEWAIT_EXIT
The QP associated with a connection has exited its timewait state and is now
ready to be re-used.  After a QP has been disconnected, it is maintained in
a timewait state to allow any in flight packets to exit the network.  After
the timewait state has completed, the rdma_cm will report this event.
.SH "SEE ALSO"
rdma_ack_cm_event(3), rdma_create_event_channel(3), rdma_resolve_addr(3),
rdma_resolve_route(3), rdma_connect(3), rdma_listen(3), rdma_join_multicast(3),
rdma_destroy_id(3), rdma_event_str(3)
